A typical internal-combustion engine utilizes a plurality of pistons to drive a crankshaft. Each of the pistons is positioned within a cylinder in the engine for reciprocal movement between a top and a bottom position within the cylinder as a result of volatile fuel being burned within the chamber defined by the cylinder. The fuel burning process generates high-pressure gases within the chamber, which drives the piston downward within its cylinder, thereby causing the crankshaft to turn. The momentum of the crankshaft and the turning forces applied thereto by other pistons will return the pistons to the top position within the cylinder. Typical engine pistons reciprocate within their cylinders thousands of times per minute, and each piston is subjected to very high pressures and temperatures. Accordingly, the pistons must be able to operate in these severe environments throughout the life of the engine.
A typical piston has a cylindrical piston head with annular piston rings installed in grooves extending circumferentially around the piston head. The piston head and rings are shaped to fit into the cylinder such that the rings engage the cylinder walls as the piston reciprocates. The piston rings maintain compression within the chamber during certain portions of the piston's travel within the cylinder to maximize the power generated. Although lubrication is provided, the rings still are subject to wear over time because of the constant sliding contact with the cylinder walls. As such, the piston rings will require replacement when sufficiently worn.
As the piston reciprocates within the cylinder, the top surface of the piston head is subject to the severe conditions created when fuel is sprayed into the chamber above the piston and ignited by a spark from a spark plug. The explosive reaction creates very high temperatures and pressures in the chamber and on the piston. As a result of these severe conditions, the piston head also wears over time and may require the repair or replacement of the piston.
When the rings and the piston head wear, compression within the cylinder decreases, thereby decreasing the horsepower generated from the engine. Also, fuel economy is lessened and smoke created by oil blown by the rings increase. In a racing vehicle such as a drag racing car, the loss of horsepower is crucial and can make the difference between winning and losing a race. As a result, extreme attention is paid to the condition of the pistons and rings.
The process of changing the piston or the rings is very labor-intensive because each worn or damaged piston must be removed from its cylinder. The piston has a piston skirt which includes two bosses with coaxial bores adapted to receive a piston pin which connects one end of a piston rod to the piston. The piston rod is connected at its opposite end to the crankshaft. The removal process typically requires gaining access to the bottom of the vehicle by lifting the car off the ground, draining the oil from the engine, removing the oil pan, and exposing the crankshaft and the bottom ends of the cylinders. Then, each desired piston rod must be disconnected from the crankshaft so the piston and piston rod can be pushed out the top end of the cylinder, which is made accessible by removing the engine's cylinder head assembly. After the piston has been removed, the worn rings may be changed or repaired. If the piston's head has been extensively worn or damaged, the piston must be separated from the piston rod, replaced and reconnected. Then, the piston with its rings and the piston rod assembled thereto must be reinserted into the cylinder and the piston rod reconnected to the crankshaft. Thereafter, the engine must be reassembled.
The process of removing, repairing or replacing one or more pistons and reassembling the engine must be performed manually and can take a considerable amount of time. The process can take a very experienced team of mechanics over four hours for a drag racing car. In certain conditions, such as in between drag races, time is a precious commodity and insufficient time may be available to complete a ring replacement job. In a conventional automobile, the average mechanic takes all day to remove and replace one or more pistons in an engine. This extremely lengthy process results in an extremely expensive repair for the customer.